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There are many ways to layout your E10 disks... is anyone using JBOD for Exchange 2010 within a DAG?

Is the failure of a node completely transparent to the end user?
Are transactions ACID compliant? .. in other words will an in-flight transaction be repeated/resumed on the failover node?

I'm aware RAID could be used within a JBOD, but some people here may not know that Microsoft has a proposed raidless-JBOD architecture with Exchange 2010 for the mailbox role. In the event an array or node fails, the CAS server will failover to a different server hosting a replica of the JBOD data.

I'm only interested in answers that take into account JBOD with the new DAG concept, does it work in the real world, and is anyone doing it.

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I would never run a production server without RAID; just my 2 cents. HDs are the most likely part to break, and RAID will prevent downtime on the particular server more than any other redundancy. – Chris S Sep 9 '10 at 15:26

ONLY ever consider using JBOD if you are going to have multiple Exchange Servers. As has already been pointed out, if one of those disks dies, so does your Exchange server.

You should set up DAGs on your mailbox servers to host multiple copies of your databases, so if one mailbox server goes down your mailbox databases are not lost and another mailbox server will take over as the active copy.

You'll also need multiple client access servers to ensure your users can still get their mail. If you do this, be sure to set up a CAS Array so if a client access server goes down, your users are automatically redirected to another Client Access server.

Multiple hub servers will also required, but there shouldn't be much configuration involved in setting those up since Exchange should just find one.

Provided that you have DAGs and CAS Arrays set up, it is all transparent to end users. They might get brief Connection to Microsoft Exchange server has been lost and Connection to Microsoft Exchange server has been restored messages, but that should be all over very quickly.

With regards to "is Exchange ACID compliant", the answer is yes. Exchange uses a write-ahead transaction log, so transactions are guaranteed. If Exchange goes down in the middle of a transaction, it will attempt recovery and replay the transaction when it is started back up. If this fails, the transaction is discarded.

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I'd +1 your answer but I don't have enough rep to do so. – TLDR Sep 9 '10 at 13:16

For which part of Exchange 2010? If you put your main database on a JBOD drive, and any one of the underlying real drives fails, the database is gone (i.e. you will need to recover it from your backups), since there is no redundancy in JBOD. For the main database you really need a RAID level with redundancy (i.e. RAID1 or higher).

However, a JBOD device can be useful for temp files.

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@wolfgansz - Microsoft is recommending JBOD's within a DAG for Exchange 2010.. I'll edit my question so that the DAG usage is emphasized – TLDR Sep 9 '10 at 13:09
Ah, that DOES make a difference. When using a DAG, that effectively introduces the redundancy which otherwise is provided by the RAID array. Using a JBOD in a DAG will probably work. To answer your question as such: we use RAID10 arrays in our DAGs. – wolfgangsz Sep 9 '10 at 13:28

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